0
Basic Machine Tool
Operation Guide
Florida Tech
Machine Shop
College of Engineering
Sept. 2006
1
Table of Contents
• Florida Tech Machine Shop
Rules...
2
• Approval to Work Process...3
• Power Tool Safety...4
I. Forms...
•
Training Record•
Student Contract•
Machine Shop Work Order•
Materials Request Form5
6
7
8
10
II.
Measuring... 13
III.
Using Calipers... 23
IV.
Layout... 26
V.
Taps and Dies... 32
VI.
Band Saw... 38
VII.
Lathe... 43
VIII.
Manual Mill... 49
IX.
Surface Grinder... 54
X.
Table Saw... 58
2
Florida Tech
MACHINE SHOP RULES
1. Students are not allowed to work without a supervisor in the Machine Shop. An approved Florida Tech paid employee must be present at all times.
2. When working in the shop two people must be present at all times. 3. Safety glasses must be worn at all times.
4. No sandals or open toes shoes. Work boots or street shoes only.
5. Material Safety Data Sheets must be supplied on materials not listed in shop MSDS book before work can begin.
6. DO NOT enter the shop under the influence of drugs or alcohol
7. All metal scrap and cuttings are to be disposed of in the proper recycling drum. Do not put trash or metals of unknown composition into the recycling drum. 8. Do not throw anything away unless you are sure that it is garbage first. Please the
ask Supervisor.
9. Do not enter material storage/staging area without permission
10. Accidents, machine problems, must be reported immediately to the supervisor. The Lab Director and faculty will be notified to determine possible disciplinary action when failure to report a problem promptly, lying, or false statements take place.
11. All students must complete a training course to be allowed to operate the equipment. Untrained students must be under direct supervision as assigned by the shop supervisor.
12. All trained students are listed on the Machine & Welding shop website. 13. The Supervisor must check all machine setups before you begin machine
operation.
14. Trained students and wok studies are required to report rule breaking, improper machine operation; any arguing with a work-study is not tolerated, they help operate the shop. Problems should be directed to the supervisor.
15. No arguing or horseplay in the shop
16. Work Studies should set an example for shop workers. Therefore rule breaking, repeated improper shop practice would be reason for dismissal and disciplinary action. Improper actions by a work- study should be reported to the supervisor immediately
17. A fact sheet on all Approved workers will be kept. Any Individual can access his/her record at anytime, as it is a public record. You must be present when entries are made.
18. All tools must be signed out and returned (this includes cutting tools) before use outside of the shop area. You must get the shop supervisor approval before leaving shop with a tool.
19. Students who do not return tools will be subject to university disciplinary action. 20. All who enter the shop all must report in with the shop supervisor.
I _________________________________ (print name) understand that I must follow all the above safety regulations when working in the machine shop
Student Signature ________________________________________ Date___________ Approved By ____________________________________________ Date __________
3 • Walk In and Work Request Rules
1. EVERY ONE MUST WEAR SAFETY GLASSES and PROPER SHOES.
2. Walk-in jobs must be simple and not require more then 1 to 2 hours of machine or bench time. Work must not be dangerous to equipment or personnel.
3. Supervisor has right to refuse any walk in work.
4. Shop fee must be agreed on or waived before Job is started.
5. All work to be performed in the shop must be written on the sign in sheet or processed on a work order. Only walk in work that will take a minimal time (less than 2 hrs) can be written up on the sign in sheet.
6. Work request forms must be completed, signed by Lab Director before work can begin.
7. All material, cutting tools, or hardware cost must be recorded on your work request or should be paid for on in advance, unless approval was given by the Director of Laboratories.
8. Jobs are done on a first come first serve basis. Problems causing work stoppage that are not the fault of the Florida Tech Machine Shop may cause the job to go to bottom of the schedule.
9. Projects cannot be kept in shop area without permission of the Director of
Laboratories or shop supervisor. Senior Design projects will have space assigned to complete the project.
10. Damage to tool is responsibility of department that is requesting work and should be recorded on work request. Damage to tools should be reported to supervisor immediately for initiating a replacement.
11. Personal work is only allowed upon approval of the Lab Director and Supervisor . 12. Class projects cannot be done in shop unless students have completed shop
training. However, shop training can be part of class syllabus.
13. Dropping off Items or Work Requests at the shop office. An individual dropping off anything at shop must sign in and give a description of action as well as contact info.
14. The Florida Tech Machine Shop will no longer donate parts, hardware, raw material, or tools to projects or individuals unless special permission from the Lab Director is given.
15. The Florida Tech Machine Shop may request complete design disclosure. All assembly, detail drawings, method of operation sheets, parts list, and other specifications (physical parts may need to be supplied) before attempting to build your project. Failure to supply these criteria may be reason to not supply support for a project.
This rule is used for manufacturing time constraints. We do not want to attempt a project when the engineering is not complete.
4
POWER TOOL SAFETY
Safety Tips:
• Use the proper tool for the job
• Never carry a tool by the cord or hose
• Keep cords and hoses away from heat, oil, or sharp edges
• Disconnect tools when not in use, before servicing and when changing accessories • Keep all guards in place and make sure they are working properly
• Wear proper apparel. Loose clothing, long hair, and jewelry can become caught in moving parts
• Wear personal protective equipment, including safety glasses and hearing protection
Take these precautions when using these power tool types:
Electric
• Make sure tools are grounded
• Use double-insulated tools when possible
• Do not use electric tools in damp or wet locations, and store the tools in a dry place • Never yank the cord to disconnect it from the receptacle
Hydraulic
• Use approved fire-resistant fluid rated for the most extreme temperatures to which it will be exposed
• Do not exceed the manufacturer’s recommended safe operating pressures
• Do not check for leaks using your hands because fluid under pressure may puncture skin
PNEUMATIC
• Always wear eye and hearing protection
• Use a safety clip or retainer to prevent attachments, such as chisels on a chipping hammer, from being unintentionally shot from the barrel
• Fasten air hoses together securely with wire or a locking device
FUEL
• Store and transport fuel only in containers approved for this application • Shut off the engine and extinguish all open flames before refueling
5
6
Florida Tech Machine Shop Training Record
Student Phone Email Age Major__ _Year___
Shop Safety Rules_________ Procedures___________
Drawing & Manufacturing Basic Dimensioning_________ Design Issues____________ CAM___________ Lab/Software____________ Plotter___________
Precision Instruments Micrometers_____Calipers___Gage Blocks____Gage Pins____Layout__
Height Gage____
Cutting Tools Milling Cutters _________ Drills _________ Reamers _________ Carbide Tooling __________ Turning Tools _______
Milling Machine Machine Operation_________ Basic Setup _________ Milling / Fly Cutting _________ Drilling________ Boring___ Skills Test_____ CNC Basic
Operation__ Horizontal Mill ________
Saws Vertical ____Horizontal ____Blade Change/Blade Selection ______ Speed Selection _________
Welding Machine Operation __________ Machine Set Up __________ Safety Operations _________
Cutting torch Basic Operation, Set Up _________ Regulator Set Up _________ Safety Operations _____
Lathe Machine Operation_________ Basic Setup _________ Basic Turning /Cutter Geometry _________ Drilling________ Boring____Skills Test_________ CNC Basic Operation__________
Hand Tools Filing ____Deburing ___Air Tools _____ Punching __ Hand Tapping ___ Power Tools _____
Bench grinder& sander Operation _______
Sheet metal Shearing _________ Bending ______ Rolling ______ General practice___
7
Florida Institute of Technology
College of Engineering
Student Contract
I ____________________am certified to operate the following machines: (Check one or more of the following)
Milling Machine Drill Press
Band Saw Bench Grinder and Belt Sander
CNC Milling Machine Lathe
Circular Saw Hand Drill
Router Jig Saw
Chop Band Saw
Certified Safe operation of the above equipment ________________________________
I understand that I must follow all the safety regulations when working in the machine shop. Which includes the following:
1. There must be at least two people in the shop at all times. I will not work in the shop alone
2. I will wear safety goggles at all times
3. I will leave the shop clean and return all the tools I have borrowed 4. I will report any tools that are broken, or missing
5. I will remove any rings, watches, or any jewelry that I am wearing 6. I will tie down any loose clothing and roll up my long sleeve shirt 7. I will not smoke in the machine shop or the building
Student Signature ________________________________________ Date___________ Approved By ____________________________________________ Date __________
8
FLORIDA TECH INTERNAL MACHINE SHOP WORK ORDER
BUILDING 538 DATE ___________
1. PRINT NAME of Person requesting work: _____________________________________ (Check/Complete only one of the following:)
A. [ ] Student Project: ____________________________________ Instructor Approval: ____________________________________ (Signature) B. [ ] Research Project: ____________________________________ (Project Number)
Principal Investigator Approval: ____________________________________ (Signature)
__________________ _________________________ Department Charge Code & Number
Department Head Approval: _____________________________________ 2. (a) Job Description (add more sheets if necessary):
________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ ________________________________________________________________________ (b) Drawing attached: [ ] Yes [ ] No
(c) Person to contact when completed: ______________________________________ Tele. No. ________________________
(d) Date Required: ______________________________________________________ 3. Estimated (a) Cost of Material___________________________________________ (b) Shop Time ______________________________________________ (c) Process Engineering Time __________________________________
9 4. MACHINE SHOP USE ONLY:
(A) TIME/DATE RECEIVED: ___________________________ JOB NO.______ (B) TIME/DATE COMPLETED:
_____________________________________________ (C) ACTUAL COST OF MATERIAL:
_________________________________________
(D) ACTUAL SHOP TIME: _______________________________________
Approval to do the work: _____________________________________ Date _________ Director of Labs or Machine Shop Supervisor
10
College of Engineering
Materials Request Form
Name____________________ Date____________ Phone______________ e-mail__________
(Check/complete only one of the following:)
A. [ ] Student Project_______________________ (Course Number) Instructor Approval __________________________________________ (Signature) B. [ ] Research Project______________________ (Project Number)
Principal Investigator Approval______________________________
(Signature)
C. [ ] Other___________________
____________________________ ________________________
(Academic Unit) (Budget Charge Code)
Academic Unit Approval ___________________________________________
(Department Head or Program Chair Approval)
Type of Material Required_________________________________________________ Quantity __________________
Dimensions: (Material estimation must be done in standard sizes-Reference Alro Catalog in Library) Height______________________________ Width______________________________ Length_____________________________ Thickness___________________________ Shape______________________________ Part #______________________________ Source______________________________ Page #______________________________ Company Contact _______________________________ Phone # of Company_____________________________
Address of Materials Company_______________________________________ __________________________________________________________________
11
Other Specifications______________________________________________________ ________________________________________________________________________ ________________________________________________________________________ Estimated Cost for Material________________________________
Date required________________________________________
Request forwarded to Director of Laboratories – College of Engineering
Additional Items:
Type of Material Required ________________________________________________ Quantity __________________
Dimensions: (Material estimation must be done in standard sizes-Reference Alro Catalog in Library) Height_______________________ Width______________________________ Length_______________________ Thickness___________________________ Shape________________________ Part #______________________________ Source_______________________ Page #______________________________ Company Contact _____________ Phone # of Company__________________ Address of Materials Company_____________________________________________ ________________________________________________________________________
Other
Specifications____________________________________________________________ ________________________________________________________________________ ________________________________________________________________________
Estimated Cost for Material________________________________ Date required________________________________________
Type of Material Required ________________________________________________ Quantity __________________
12
Height_______________________ Width______________________________ Length_______________________ Thickness___________________________ Shape________________________ Part #______________________________ Source_______________________ Page #______________________________ Company Contact _____________ Phone # of Company__________________ Address of Materials Company_____________________________________________ ________________________________________________________________________
Other
Specifications____________________________________________________________ ________________________________________________________________________ ________________________________________________________________________
Estimated Cost for Material________________________________ Date required__________________________________
Request forwarded to Director of Laboratories – College of Engineering
13
14 Industry regularly makes
measurements to a millionth (0.000001) part of an inch. A distance this small is called a MICROINCH. If the microinch were the thickness of a dime, and inch would be as high as four Empire State Buildings.
In addition to the English
measurement (inch, foot, etc.), industry, to a limited extent, also uses the metric system of measurement (meter). The United States has tentatively adopted the simplified and clarified metric system devised by the International Standards Organization (ISO). All of the states are in the process of converting to the metric system of the next several years.
Regardless of how fine industry can measure, the job at hand is to learn to read the rule to 1/64 in.; progress through 1/1000 (0.001) in. by
micrometer and Vernier type measuring tools; and finally to 1/10000 (0.0001) in. by the Vernier scale on the hub of some micrometer calipers.
Metric based measuring tools will offer no problems. As a matter of fact, many think they are easier to learn to read than inch based measuring tools.
The Rule Types of Rules
The steel rule, often incorrectly referred to as a scale, is the simplest of the measuring tools found in the shop. See Fig. 4-1 for the three basic types of rule graduations. A few of the many rule styles are shown in Fig. 4-2a to 2g.
Reading The Rule
A careful study of the enlarged section of the rule, Fig 4-3, will show the different
fractional divisions of the inch from 1/8 to 1/64 in. The lines representing the divisions are called GRADUATIONS. On many rules, every fourth graduation is numbered on the 1/32 edge, and every eighth graduation on the 1/64 edge.
The best way to learn to read the rule is to: 1. Become thoroughly familiar with the 1/8
and 1/16 measurements.
2. Do the same with the 1/32 and 1/64 measurements
3. Practice until you become proficient enough to read measurements accurately and quickly.
Some steel rules (inch based) are graduated in 10ths, 20ths, 50ths and 100ths. Additional practice will be necessary to read these rules accurately and quickly.
Fractional measurements are always reduced to the lowest terms. A measurement of 14/16 is 7/8, 2/8 is 1/4 etc.
Care of the Rule
The steel rule is precision made and, like all tools the quality of service depends upon the care it receives. Here are a few suggestions:
1. Use a screwdriver to loosen and tighten screws and to open paint cans. DO NOT use a rule.
2. Keep the rule clear of moving
15 as they form on the machine will not
only ruin the rule, but will prove extremely dangerous to the person attempting it.
3. Avoid laying other tools on the rule. 4. Frequent wiping with an oily cloth
will prevent the forming of rust.
5. An occasional cleaning with fine steel wool will keep the graduations legible. 6. Make it a practice to take measurements
and tool settings from the 1-in. line or other major graduation rather than from the end of the rule.
7. Store the rule separately. Do not throw it in a drawer with other tools.
16 8. Use the rule carefully so that the
ends do not become nicked or worn. 9. Use the correct rule for the job at
hand.
10. Coat the tool with wax or a rust preventative if the rule is to be stored for a prolonged period.
The Micrometer Caliper
A Frenchman, Jean Palmer, devised and patented a measuring tool that made use of a screw thread to make it possible to read measurements quickly and accurately
without calculations. It incorporated a series of engraved lines on the hub and around the thimble. The device, Fig. 4-4, called “Systeme Palmer,” is the basis for the modern MICROMETER CALIPER.
The modern micrometer caliper, known as a “mike,” is a precision measuring tool capable of measuring to 1/1000 (0.001) in. and when fitted with a Vernier scale to 1/10000 (0.0001) in. While manufactured in sizes up to 60 in., the movement of the spindle is limited to 1 in. Only the frame is enlarged.
17
Types of Micrometers
Micrometers are made in a large variety of models. A few of the more commonly used are:
OUTSIDE MICROMETER, Fig 4-5. Measures outside diameters and material thickness.
INSIDE MICROMETER. Excellent for measuring inside cylinders and rings, measuring parallel slots, and for setting calipers, gages, etc. There are two generally used styles: the CONVENTIONAL INSIDE CALIPER, Fig 4-6, whose range is extended by fitting longer rods to the micrometer head, and the JAW-TYPE INSIDE MICROMETER, Fig. 4-7. It is used in much the same manner, however, its range is limited to 1 in. Note that the scale on the
hub of the jaw type is graduated from RIGHT TO LEFT.
DIRECT READING MICROMETER, Fig 4-8. Measurements are read directly from the
numbers appearing in the opening in the frame. MICROMETER DEPTH GAUGE, Fig 4-9. Depths of holes, slots, projections, etc. can be measured with this tool. The measuring range can be increased by changing to measuring rods of longer lengths.
SCREW THREAD MICROMETER CALIPER Fig. 4-10. This micrometer has a pointer spindle and a double “V” anvil, both correctly shaped to contact the screw thread. It measures the pitch diameter of the thread in thousandths of an inch, which equals the outside diameter of the screw minus the depth of one thread.
SPECIAL MICROMETERS, Fig. 4-11. Many cutting tools have cutting edges that are uneven in number. This makes it impossible to measure their diameter with the conventional “mike.” Special micrometers have been devised to handle this and other situations.
How to Read a Micrometer
The principle of the micrometer, a sectional view is show in Fig 4-12, is based on a very accurately made screw thread that rotates in a fixed nut. The screw thread is ground on the SPINDLE (C) and is attached to the THIMBLE (J). The spindle advances or recedes from the
19 ANVIL (B) by rotating the thimble. The
threaded section has 40 threads per inch; therefore, each revolution of the thimble moves the spindle 1/40 in. (0.025).
The line engraved lengthwise on the HUB is divided into 40 equal parts per inch that correspond to the number of threads on the spindle. Each vertical line represents 1/40 or 0.025 in. Every fourth division is numbered 1, 2, 3 etc., representing 0.100 in., 0.200 in. etc.
The beveled edge of the THIMBLE (J) is divided into 25 equal parts, each
representing 1/1000 (0.001) in. Each division is numbered on many micrometers, while every fifth division is numbered on others.
The micrometer caliper is read by recording the highest figure visible on the HUB, 1 = 0.100, 2 = 0.200, etc. To this number is added the number of vertical lines visible between the number and thimble edge, 1 = 0.025, 2 = 0.050, etc. To this total is added the number of thousandths
indicated by the line on the thimble that coincides with the horizontal line on the hub. See Fig. 4-13.
EXAMPLE 1:
The reading is composed of:
4 large graduations or 4 x 0.100 = 0.400 2 small graduations or 2 x 0.025 = 0.050 and 8 graduations on the
thimble or 8 x 0.001 = 0.008 Total reading = 0.458 in. EXAMPLE 2:
The reading is composed of:
2 large graduations or 2 x 0.100 = 0.200 3 small graduations or 3 x 0.025 = 0.075 and 14 graduations on the
thimble or 14 x 0.001 = 0.003 Total reading = 0.289 in. EXAMPLE 3:
The reading is composed of:
3 large graduations or 3 x 0.100 = 0.300 2 small graduations or 2 x 0.050 = 0.050 and graduations on the
thimble or 3 x 0.001 = 0.014 Total reading = 0.353 in.
How to Read a Vernier Micrometer Caliper
On occasion, it becomes necessary to measure finer than 1/1000 in. When this situation is encounter, the Vernier micrometer caliper is employed. This micrometer has a third scale AROUND THE HUB, Fig 4-14, that furnished the 1/1000 reading without estimating or guessing. The Vernier has 11 parallel lines occupying the same space as 10 lines on the thimble. The lines around the hub are numbered 1 to 10. The difference between the space on
20 the hub are those on the thimble is one-tenth of a space on the thimble or 1/10 of a
thousandth (0.001) of an inch. To read, first obtain the thousandths reading, then observe which of the lines on the Vernier scale coincide with a line on the thimble. Only one of them can. If it is line 1, add 0.0001 to the reading; if line 2, add 0.0002 to the reading, etc.
EXAMPLE: (See Fig. 4-15.) The reading is composed of:
2 large graduations or 2 x 0.100 = 0.200 3 small graduations or 3 x 0.025 = 0.075 11 graduations on the
thimble or 11 x 0.001 = 0.011 and the additional distance the
thimble has advanced beyond the 0.011 inch mark.
In this case it has advanced 0.0002 Total reading = 0.2862 in.
How to Read a Metric Based Micrometer
The metric based micrometer, Fig. 4-16, is read as shown in Fig. 4-17. If you are able to read the conventional inch based micrometer the change over to reading the metric based tool will offer no difficulties.
How to Use the Micrometer
Fig. 4-18 shows the proper way to hold the micrometer when making measurements. The work is placed into position, and the
thimble rotated until the part is clamped lightly between the anvil and spindle. Guard against excessive pressure as it will cause an erroneous reading.
The correct contact pressure will be applied if a mike with a RATCHET STOP is employed, Fig. 4-19. This device is used to rotate the spindle and insures consistent, accurate measurement by limiting the spindle pressure on the work to a definite amount, even when different machinists use the same micrometer. When pressure reaches a predetermined amount, the ratchet slips and prevents further tightening.
Some micrometers are fitted with a
FRICTION CLUTCH, Fig. 4-5. The attachment will slip the moment the correct pressure is applied and provide an accurate measurement. Whene several identical parts are to be gauged,
21 lock the spindle in place with the LOCK
NUT, Fig. 4-12 (F). When a part is gauged with the micrometer locked at the proper setting, it is quite easy to identify the piece as being oversize, correct size or undersize.
How to Read an Inside Micrometer
To get a correct reading with and INDISE MICROMETER, it is important that the instrument be held square across the diameter and positioned so it will measure the diameter on exact center. Large diameters are measured, Fig. 4-20, by holding one end of the tool in place and then “feeling” for the maximum possible setting by moving the loose end from left to right, and in and out of the hole with your free hand. The measurement is taken when no left or right movement is felt, and a slight
drag is noticeable on the in-and-out swing. It may be necessary to make several readings and average them.
How to Read the Micrometer Depth Gauge
Be sure to read the micrometer depth gauge, Fig. 4-9, correctly. Unlike the outside
micrometer, the graduations on this tool are in REVERSE ORDER. That is, they read 0, 9, 8, 7, 6, etc. The graduations UNDER the thimble must be read rather than those that are expos
23
USING
CALIPERS
24
CALIPERS
The OUTSIDE CALIPER, Fig. 5-1, is used to make external measurements where a 1/64 in. tolerance is permitted. A caliper does not have a dial or gauge which shows a
measurement, and must be used with a steel rule.
Round stock is measured by setting the caliper to the approximate diameter of the material.
Then, hold the caliper square with the work and move the caliper legs down on the stock.
Adjust the tool until the caliper points bear lightly on the centerline of the stock. The weight of the caliper should cause the tool to pass over the diameter. Hold the caliper to the rule, Fig. 5-2, to read the size.
The INSIDE CALIPER, Fig. 5-3, is used for making internal measurements where 1/64 in. accuracy is acceptable.
A hole diameter can be measured, Fig. 5-4, by setting the caliper to the approximate size of the hole, and inserting the legs into the opening. Hold one leg firmly against the hole wall, and adjust the thumbscrew until the other leg lightly touches the wall exactly opposite the first leg. The legs should “drag” slightly when moved in and out, or from side to side. Read the hole size by holding the caliper to a steel rule, Fig. 5-5.
There are times when a shaft must be turned to fit a hole, and it becomes necessary to transfer the measurement from one caliper to another. This can be accomplished quickly by setting the inside caliper to fit the hole diameter. Place one leg of the inside caliper against one leg of the outside
25
caliper, and adjust the outside caliper until the second leg lightly touches the other leg of the inside caliper.
Considerable skill is required to make accurate measurements with calipers. Much depends upon the machinist’s sense of touch. With practice, measurements to within 0.003 to 0.005 in. can be made. A micrometer or Vernier caliper should be used if greater accuracy is required.
TEST YOUR KNOWLEDGE
1. The ____________ caliper is used to make external measurements.
3. Calipers are used where ________ in. accuracy is acceptable.
2. The ____________ caliper is used to make internal measurements.
4. A _______ or _________ caliper should be used when accuracy closer than 0.003 to 0.005 is required.
26
27
LAYOUT WORK
LAYING OUT is the term used to describe the locating and marking out of lines, circles, arcs and points for drilling holes. These lines and reference points on the metal show the machinist where to machine.
The tools used for this work are known as LAYOUT TOOLS. Many common hand tools fall into this category. The accuracy of the job will depend upon the proper and careful used of these tools.
Making Lines on Metal
The shiny finish of metal makes it difficult to distinguish the layout lines from the metal. LAYOUT DYE, Fig. 6-1, is probably the easiest to use of the many coating devised to make the lines stand out better. This blue colored fluid, when applied to the metal, offers an excellent contrast between the metal and the layout lines. All grease and oil must be removed before applying the dye, otherwise it will not adhere properly.
28 In a pinch, layout fluid can be made by
dissolving the coating on spirit duplicator carbons in alcohol. Chalk can be used on hot rolled metal as a layout background.
A layout, to be accurate, requires fine lines that must be scribed or scratched in the metal. A SCRIBER, Fig. 6-2, is used to produce these lines.
The point is made of hardened steel, and is kept needle sharp by frequent honing on a fine oilstone. Many styles of scribers are available. CAUTION: NEVER CARRY AN OPEN SCRIBER IN YOUR POCKET.
The scriber is used to draw straight and gradually curved lines, circles and arcs are made with the DIVIDER, Fig. 6-3a.
It is essential that both legs of the tool be equal in length and kept pointed. The divider can be used to lay out and measure distances, Fig. 6-3b. To set the tool to the correct dimension, place one point on an
29 inch mark of steel rule, and open the divider until the other leg is set to the proper
distance, Fig. 6-3c.
Circles and arcs that are too large to be made with the divider are drawn with a trammel, Fig. 6-4. This consists of a long thin rod, called a BEAM, on which two SLIDING HEADS with scriber points are mounted. One head is fitted with an ADJUSTING SCREW. EXTENSION RODS can be added to the beam to increase the capacity of the tool.
The HERMAPHRODITE CALIPER, Fig. 6-5a, is a layout tool which has one leg shaped like a caliper, and the other pointed like a divider. The tool is used to lay out
lines parallel to the edge of the material, Fig. 6-5b, and to located the center of irregularly shaped stock.
A SURFACE GAUGE, Fig. 6-6a, is used for many purposes, but is most frequently used for layout work. It consists of a BASE, SPINDLE and SCRIBER.
An ADJUSTING SCREW is fitted for making fine adjustments. The scriber is mounted in such a manner that it can be pivoted into any position. The surface gauge can be used for scribing lines, at a given height and parallel to the surface, Fig. 6-6b. A V-slot in the base permits the tool to be used on a curved surface.
31
Steps in Making a Layout
Each layout job has its peculiarities and requires some planning before the operation can be started. Fig. 6-19 shows a typical job.
1. Study the drawings carefully.
2. Cut the stock to size and remove all burrs and sharp edges. 3. Clean the work surface of all oil and grease and apply layout dye.
4. Locate and scribe a REFERENCE or BASE LINE. Make all of your measurements from
this line. If the material has one true edge, it can be used in place of the reference line.
5. Locate the center points of all circles and arcs.
6. Use the PRICK PUNCH, Fig. 6-20, to mark the point where the center lines intersect.
The sharp point (30 to 60 deg.) of this punch makes it easy to locate this position. After the prick punch mark has been checked and found on center, it is enlarged with the CENTER PUNCH, Fig. 6-20.
7. Using the divider or trammel, scribe in all circles and arcs.
8. If angular lines are necessary, use the proper protractor type tool, or locate the correct
points by measuring, and connect them by using a rule or straightedge.
9. Scribe in all other internal openings. 10. Use only clean sharp lines.
Modern Metalworking S A F E T Y
1. Never carry an open scriber, divider, trammel or hermaphrodite caliper in your pocket. 2. Always cover all sharp points with a cork when the tool is not being used.
3. Wear goggles when grinding the points of scriber type tools.
4. Get help when you must move heavy angle plates, large V-blocks, etc. 5. Remove all burrs and sharp edges from stock before starting to work on it.
32
33
HOW TO USE TAPS AND DIES
ABOUT TAPS AND DIES:
American Standard Taps and Dies are designated according to the Metal Cutting Institute Standard System of Marking as follows:
1) Nominal size such as a fraction or number representing the major diameter of the thread.
2) Number of threads per inch
3) Symbol to identify the thread types Metric Taps and Dies are designated as follows:
1) A number representing the major diameter of the thread 2) The symbol MM indicating metric
3) A number which is the pitch (or distance from the crest of one thread to the crest of the next thread) of the thread in millimeters
TAPS
WHAT A TAP IS – WHAT A TAP DOES
A tap is a precision tool used in the cutting of an internal thread such as in a nut. Just a drill removes material to make a hole, a tap cuts material away to form a thread.
There are three basic types of hard taps: i.e., “taper”, “plug”, and “bottom” taps. The difference in these is the length of the chamfer on the starting end of the tap. “Taper” taps are chamfered for the first 6-8 threads. This makes staring easier but prevents threading close to the bottom of a hole. “Plug” taps are camfered 3-5 threads from the end. This is the optimum for starting and being able to tap close to the bottom of a hole. “Bottoming” taps have a very short camfer, 1 1/2-3 threads, and will tap as close to the bottom of a hole as practical; however, to do this requires starting the thread with a “plug” or “taper” tap first.
TOOLS REQUIRED TO MAKE A THREADED HOLE 1) A Tap of the correct size and thread form
2) A Tap wrench
3) Proper drill size or hole size 4) Lubrication or cutting oil
The correct drill or hole size is of great importance in producing satisfactory threads. The Tap Drill Chart (see later pages) provides a ready reference table of the correct drill sizes. Use of a smaller drill than specified does not provide a stronger or tighter thread. It only serves to overload the tap and cause undue breakage. Lubrication of the tap while cutting threads is important in producing smooth threads and maintaining long tap life. Refer to the lubrication section for recommendations.
RENEWING THREADS
34
size and select the proper tap. Next carefully start the tap into the pre-threaded hole and proceed in the same manner as when cutting new threads. Some materials are case hardened and if a tap is forced into work in this type, damage to the tap will result. A simple file test will determine whether or not to proceed. If material can not be easily filed, do not attempt to rethread it.
CUTTING INTERNAL THREADS
The tap is held by the square in tap wrench and is started into the hole by turning clockwise for right hand threads. Care must be taken to start the tap straight in line with the hole. As the tap is turned it cuts into the metal and starts to lead into the hole. The metal chips flow into the flute spaces and will cause the tap to turn hard unless the chips are broken. The chips are broken and pressure on the tap is released by reversing the tap direction every ¼ or ½ a revolution depending on the material being tapped. This action is continued until the tap passes through the part or the desired depth of the thread has been reached. In cases where it is necessary to tap a hole that does not pass through the part, or so called blind hole, be sure to provide clearance at the bottom to accommodate chips and the camfer section of the tap.
WHEN USING TAPS
DO drill correct size hole (see chart) DO countersink hole before tapping
DO keep tap straight in line with the hole being tapped DO reverse tap during use to break up chips
DO use correct lubrication
DO provide rigid holding of part being tapped
The operation of any cutting tool can result in foreign objects being thrown into the eyes, which can result in severe eye damage. Always wear safety glasses or eye shields before starting cutting tool operation.
DON’T use too small a tap drill
DON’T crowd tap – Tap should be turned backwards slightly every ¼ to ½ turn to clear chips
from tap flutes.
DON’T fail to clean tap before storage
MAINTENANCE
The importance of using a sharp tap cannot be over emphasized. As taps require precision sharpening equipment, it is recommended that dull or damaged tools be replaced.
DIES
35
A die is a precision tool used in cutting external or outside threads. Dies cut external threads such as on a bolt.
TOOLS REQUIRED TO CUT AN EXTERNAL THREAD 1) A die of the correct size and thread form
2) A die stock to hole the die 3) Lubricating or cutting oil HOW TO USE A DIE
After selecting the proper die, position and hold in the die stock, with the starting side next to the guide, by means of a set screw which tightens against the edge of the die. Next place the adjustable guide side of the die stock on the rod or bolt to be threaded.
With the rod or bolt in position, adjust the guides by turning the chuck plate counter clockwise until guides touch the rod of bolt. Clamp plate is then held in place by tightening the two knurled screws. The adjustable guides properly set assure cutting straight threads.
CUTTING EXTERNAL THREADS
Rigidly secure the correct size rod or bolt, preferably 0.005 to 0.010 undersize and beveled for ease in starting and turn the die clockwise. As the die starts to cut, chips will flow and should be broken by reversing every ¼ to ½ turn. Periodic application of cutting oil will help in cutting smooth threads and in prolonged die life. Continue the forward and reversing action until the desired length of thread has been cut.
RENEWING THREADS
Damaged threads are readily repaired by proceeding as for cutting new threads. Care should be taken to start the die in the previously formed thread.
WHEN USING DIES
DO select the right size die
DO keep die at right angle to work piece DO use correct lubrication
DO chamfer or bevel end of work before threading DO clean and store dies in proper spaces after use
The operation of any cutting tool can result in foreign objects being thrown into the eyes, which can result in severe eye damage. Always wear safety glasses or eye shields before commencing cutting tool operation.
DON’T crowd die – die should be turned backwards slightly every ¼ to ½ turn to clear chips
from die
DON’T jam the die against the head or shoulder when threading close.
1) Steel Lard oil, cutting oil, or Crisco 2) Cast Iron Dry or air blast
3) Aluminum Kerosene or Kerosene lightly mixed with lard oil
36
5) Magnesium Kerosene
6) Zinc Kerosene
7) Bakelite Dry
8) Hard Rubber Dry
9) Bronze Kerosene or Kerosene mixed with lard oil 10) Stainless steel Kerosene mixed with lard oil
Additional lubricants for production or industrial uses may be obtained by consulting commercial distributors of oils and greases.
TAP SIZE DEC EQUIV. FRAC DRILL SIZE
TAP SIZE DEC. EQUIV FRAC. DRILL SIZE
TAP SIZE DEC EQUIV FRAC DRILL SIZE 4 – 40 0.0890 3/32 5/8 – 11 0.5312 37/64 7mm -1 0.234 15/64 6 – 32 0.1065 7/64 5/8 – 18 0.5781 19/32 8mm – 1 0.277 9/32 8 – 32 0.1360 9/64 11/16-11 0.5937 5/8 8mm-1.25 0.265 17/64 10-32 0.1590 5/32 11/16-16 0.6250 21/32 ¼-19BSP 0.453 29/64 10-24 0.1495 5/32 ¾-10 0.6562 11/16 9mm-1 0.3125 5/16 12-24 0.1770 11/64 ¾-16 0.6875 49/64 9mm-1 0.3125 5/16 ¼-20 0.2010 13/64 7/8-9 0.7656 13/16 10mm-1 0.359 23/64 ¼-28 0.2130 7/32 7/8-14 0.8125 7/8 10mm-1.25 0.3437 11/32 5/16-18 0.2656 17/64 1 in. -12 0.9219 59/64 10mm-1.5 0.339 11/32 5/16-24 0.2656 17/64 1 in. -14 0.9375 15/16 11mm-1.5 0.375 3/8 3/8-24 0.3281 21/64 3mm-0.5 0.0995 3/32 12mm-1.5 0.406 13/32 3/8-16 0.3125 5/16 3mm-0.6 0.0937 3/32 12mm-1.75 0.406 13/32 1/8 PIPE 0.3125 5/16 3.5mm-0.6 0.116 1/8 14mm-1.25 0.515 33/64 ¼ PIPE 0.437 25/64 4mm-0.7 0.1285 1/8 14mm-2 0.469 15/32 7/16-20 0.3906 3/8 4mm-0.75 0.125 1/8 16mm-1.5 0.578 37/64 7/16-14 0.3750 27/64 4.5mm-0.75 0.141 9/64 16mm-2 0.656 35/64 ½-13 0.4219 29/64 5mm-0.8 0.166 11/64 18mm-1.5 0.6614 21/32 ½-20 0.4531 31/64 5mm-.09 0.161 5/32 18mm-2.5 0.609 39/64 9/16-12 0.4844 33/64 6mm-1 0.196 13/64 1/8-28BSP 0.3281 21/64 9/16-18 0.5156 17/32 6.3mm-1 0.213 7/32 1 in.-8 0.8750 7/8 MAINTENANCE
The importance of using sharp dies cannot be overemphasized. As dies require precision sharpening equipment, it is recommended that dull or damaged tools be replaced.
37
EXTRA INFORMATION
EFFECT OF HOLE OR BOLT SIZE ON HEIGHT OF THREAD
When cutting threads, if the tap or die cuts awat metal the full form or depth of the thread, the result is 100% height of thread on the work. Therefore, the height of thread is determined by the size of the drilled hole for tapping, or the size of bolt or rod when using a die. If the size of the hole is the same size as the minor diameter of the tap, the thread produced would be 100% height.
When the hole is larger than the minor diameter of the tap, or the size of the bolt or rod is less than the major diameter of the die, the height of the thread cut will be less than 100%. Thus to vary the height of the thread, one must vary the size of the drilled hole or size of the bolt or rod.
A 100% thread is only 5% stronger than a 75% thread height, but requires 3 times the power to turn the tap. A 100% thread height does not give a tighter fit. It only serves to overload the tools and possibly cause premature tool failure.
The recommended thread height is 75% for average use and the Tap Drill Reference Chart gives the correct drill size for each size tap. One should also remember in preparing bolts or rods for cutting of the external thread, the diameter of the bolt or rod should be from 0.005 to 0.010 under the nominal size.
The thread gauge will help in determining the correct number of threads per inch on a bolt or nut, or pitch on metric sizes. The gauge is provided with blades each marked with a number corresponding to the threads per inch or pitch. For example: “16” on the blade means 16 threads per inch. The part is checked by placing the correct blade in such a manner that all teeth or notches align properly with the threads on the bold or nut. As a substitute for a thread gauge, a tap may be used in the same manner as described above.
The bolt diameter is established by measuring the outside diameter with micrometers. Normally bolts are manufactured with the diameter slightly under the nominal size. For
example; a 5/16 inch bolt will probably measure 0.305, instead of 0.3125, when measure in this manner.
LUBRICATION
Selection and application of the proper lubricant has a very important bearing on the success of the thread cutting operation. Longer tap and die life plus smoother, cleaner, and more
accurately formed threads will be the benefits. Once the proper lubricant has been selected it should be directed with an oil can, brush, or other convenient method to the cutting edges during threading operation. Recommended lubricants most readily available for the home work shop use are listed with the materials to be threaded.
38
39
Safety Instructions
1. Read and understand the owner’s manual before operating the machine 2. Always wear safety goggles when operating this machine
3. Be positive the saw blade is installed properly – teeth pointing downward toward the table – before operating this machine
4. Be sure blade tension, blade guides, and thrust bearings are properly adjusted before operation of the machine
5. Always adjust the upper guide to clear the work piece by a ¼ of an inch
6. Minimize potential injury from contact with the saw blade by keeping fingers at a safe distance away
7. Maintain control of the work piece at all times. Hold firmly against the table. Use a vice 8. Be attentive to thin cut off pieces hitting the end of the slot in the insert or jamming in the
slot
9. Get help when cutting heavy material
10. Clean oil and grease from the floor around the work area 11. Stop the machine before making adjustments
40
Band Saw
The advantage of using the Band Saw:
1. Faster Cutting – the long blade moves in only one direction, and being continuous, can be run at much higher speeds as the blade rapidly dissipates the heat generated in cutting. The horizontal band saw in the shop can be run at speeds between 80 and 200 feet per minute. 2. Precision – The blade can be guided more accurately than the blade on the reciprocating saw
and can utilize a finer blade for a given piece of material. It is common practice to cut directly to the line when using a band saw. The vise on the horizontal saw will increase the accuracy of any cutting operation. The vise can be opened to five inches and can be tilted to cut at angles between 0 and 90 degrees.
3. Little Waste – The small cross section of the band saw blade make smaller and fewer chips for a given length or thickness of material. The blades are made from tungsten and
molybdenum steel and with tungsten carbide teeth on alloy steel backs. The carbide tip blades are more expensive. You can buy three tungsten blades for the price of one carbide tipped blade.
How to Select a Blade –
Choosing the proper blade is important. Always use the three- tooth rule. There must be at least three teeth in contact with the work at all times, but no more than 18.
1. Large pieces and soft materials require coarse teeth. 2. Thin work and hard materials require a fine tooth blade.
3. For best cutting action, apply heavy feed pressure on soft materials and large work. 4. Light Pressure on hard materials work and small work.
The number of teeth per inch is also important, they can range from 3 to 18 teeth per inch. 1. Use a 3 tooth blade when cutting 2” thick piece of wood
2. An 8 tooth blade for ¾” of stock 3. A 16 tooth blade for ¼” stock
These 3 examples leave 4-6 teeth on the work at all times. If there are too many teeth cutting the material, the saw blade can bind, or it will make wavy cuts in the material.
1. From figure 1, the Standard Tooth is best for cutting ferrous metals.
2. The Skip Tooth blade pattern is best suited for cutting aluminum, magnesium, copper and soft brass
41
4. The width of the blade can range from 1/8” to ¾”. As shown in the figure below, narrower blades can turn with a tighter radius. But for accuracy, smoothness, and blade life, use the widest blade possible.
The Horizontal Band Saw
The Horizontal Band Saw uses a blade that has the size of ½” x 0.025” x 641/2”. Use the following procedure to change the blade.
1. Make sure the machine is unplugged
2. Raise the cutting head to the vertical position 3. Remove the guard
4. Loosen the blade guide , until the blade can be removed.. Remove the blade. 5. Install the new blade. The blade teeth should look like the following diagram.
42
6. Make sure the blade is not twisted, tighten the adjusting knob. The blade should be able to flex. Improper blade tension ruins blades and can cause early failure of the wheel bearings. Check with a shop assistant, if you are unsure.
7. Replace the guard
8. When starting the machine again, make sure that the band does not fall off.
Vertical Band Saw-
The finish and accuracy of the Vertical Band Saw can be held to within 0.010 to 0.0015 in. This accuracy eliminates or minimizes many secondary machining operations. Finishing operations can be performed with a file or the milling machine. Abrasive and brittle materials and the hardest steels can be cut rapidly and economically on the band saw by substituting a diamond edge blade for the conventional blade.
The blade for the vertical band saw is ¼” wide, 6 teeth per inch and 80 inches long.
Use the following procedure to change the blade. 1. Unplug the machine
2. Remove the front cover
3. Loosen the blade tension adjustment knob on the top of the machine. Keep turning the knob until the blade can be removed
4. Place the new blade with the teeth pointing downward. As in the diagram at the top of the page.
5. Make sure the blade is in the blade guide and that the blade is not twisted on the wheels
6. Tighten the blade adjustment knob. Again the proper blade tension is important, the blade should be able to flex. Improper blade tension can ruin the blade the blades and can cause early failure of the wheel bearings. Check with a shop assistant, if you are unsure
7. Replace the front cover
43
44
SAFETY
1) Do not attempt to operate the lathe until you have been checked out on it and are thoroughly
familiar with its operation.
2) Dress appropriately. Remove your necktie, sweater, wrist watch and rings. Wear an apron
or a properly fitted shop coat. Safety goggles are a must.
3) Clamp all work solidly. Use the correct size tool or work holding device for the job. Get
help if you must use heavy chucks or attachments.
4) Check your work frequently when it is being machined between centers. The work expands
as it heats up and could damage the tail center if it overheats.
5) Replace all guards before starting to work. The guards should only be removed to make
adjustments, and then with the power turned off at the main electrical panel to prevent the machine from being turned on accidentally. Replace the guards immediately after the adjustments have been made.
6) Return all unnecessary tools to the proper storage area. Remove all other tools from the
immediate work area.
7) Turn the chuck or faceplate by hand to be sure there is no binding or danger of the work
striking any part of the lathe.
8) Stop the machine before making adjustments or measurements.
9) Remember that the chips are razor sharp. Do not attempt to remove chips with your fingers.
Stop the machine and use pliers to remove them.
10) Support all work solidly. Do not permit small diameter work to project too far from the
chuck without support from the tailstock center.
11) Be careful not to run the cutting tool into the chuck or dog. Check out any readjustment of
work or tool to be sure there is ample clearance between the tool and the chuck or dog, when the tool has been moved left to the farthest point that will be machined.
12) Do not use cotton waste or rags to wipe grease or oil from the work surface unless the
machine is stopped. Keep brushes used for cleaning and to apply coolant, clear of work when knurling.
13) If work must be removed from the lathe, or repositioned in the chuck, always move the
cutting tool clear of the work or reverse it in the tool post to prevent it from cutting you accidentally.
14) Do not talk to anyone, nor permit anyone to fool around the machine while you are operating
it. You are the only one who should turn the machine on or off, or make adjustments to the lathe while you are operating it.
15) Never attempt to run the chuck on or off the spindle by using power. It is also a dangerous
practice to stop the lathe by reversing its direction of rotation.
16) You should always be aware of the direction and speed of the carriage or cross-feed before
engaging automatic feed.
17) Never leave the key in the chuck. Make it a habit never to let go of the key until it is out of
the chuck and clear of the work area.
18) Tools must not be placed on the lathe ways. Use a tool board or place them on the lathe tray. 19) Do not wrap the cord around your hands when cleaning the lead screw. Grip it lightly
between the fingers so if it catches on the screw it will slip safely out of your hand.
20) Never use a file without a handle.
21) Stop the machine immediately if some odd noise or vibration develops while you are
operating it. If you cannot find what is causing the trouble, get your instructor. Under no condition should the machine be operated until the trouble has been found and corrected.
45
22) Remove all burrs and sharp edges from the piece before removing it from the lathe.
23) Plan your work thoroughly before starting. Have all of the tools that will be needed at hand
before commencing work
24) Be careful when you clean the machine. As stated before, chips and shaving are sharp and
will cause serious cuts if you attempt to remove them with your hands. Use a cleaning brush, NOT A DUST BRUSH, for the job. NEVER USE THE AIR HOSE. The flying chips may injure someone.
PREPARING THE LATHE FOR OPERATION
1) Clean and lubricate the lathe. Use the lubricants specified by the manufacturer.
2) Turn the spindle by hand to make sure it is not locked in back gear. Set the drive mechanism to the desired speed and feed.
3) Place all guards in position.
4) Move the carriage along the ways; there should be no binding.
5) Inspect the cross-feed and compound rest slides. Adjust the gibs if there is too much play. Do not permit excessive overhang of the compound rest.
6) Inspect the tailstock if it is to be used for any portion of the operation. Check it for alignment and use a smooth dead center.
7) Place the proper work holding attachment on the headstock spindle. Clean the threads and apply a drop of oil.
8) Sharpen the cutter bit. Clamp it in the appropriate tool holder and mount it in the tool post.
HOW TO CLEAN THE LATHE
A lathe should be cleaned after each work period. Remove chips with a paint brush – NOT YOUR HAND. Wipe all painted surfaces with a sodt cloth. To complete the job, move the tailstock to the extreme right and use a soft cloth to wipe the remaining oil, chips and dirt from the machined surfaces. DO NOT USE COMPRESSED AIR TO REMOVE THE CHIPS. The flying chips are dangerous.
The lead screw needs an occasional cleaning too. This may be done by adjusting the lathe to rotate at a slow speed and using a piece of cord. Permit the cord to feed along the threads. DO NOT WRAP THE CORD AROUND YOUR HAND because THE CORD MIGHT CATCH ON THE LEAD SCREW AD CAUSE SERIOUS INJURY!
METAL LATHE
A lathe is a machine tool in which the work is held and rotated, while being shaped by a cutting tool that is fed against the work.
LATHE SIZE
Lathe size is determined by the SWING and BED LENGTH. The swing indicates the largest diameter of work which can be turned. The bed length is the entire length of the ways, and should not be mistaken for the maximum length of metal piece that can be turned.
47
MAJOR PARTS OF THE LATHE
Each of the lathe parts fall into one of three functional categories: 1. DRIVING THE LATHE
2. HOLDING AND ROTATING THE WORK
3. HOLDING AND MOVING THE CUTTING TOOL
LATHE BED
The lathe bed is the foundation or base to which the other parts of the lathe are fitted. Carefully machined ways on top of the lathe bed, support and provide for precise alignment of the headstock and tailstock.
HEADSTOCK
The headstock contains the SPINDLE to which the various work holding attachments are fitted. The spindle is hollow with the front end tapered internally to receive tools and attachments with taper shanks. The hole permits long stock to be turned and allows a KNOWCKOUT BAR to be used to remove taper shank tools.
The spindle is usually fitted with either a tapered nose or a threaded nose. Also found in the headstock is the SPEED CONTROL MECHANISM. Power supplied by an electric motor is transmitted to the spindle by moving the belts to positions on the pulleys or by changing the gear ratio.
Slower speeds on belt driven lathes are obtained by engaging the BACK GEARS. The large gear (BULL GEAR) is keyed to the spindle and is locked to the pulley with the BULL GEAR LOCK PIN. The back gears can be engaged by disconnecting the bull gear from the step pulley by
releasing the bull gear lock pin. DO NOT ENGAGE THE BACK GEARS WHILE THE SPINDLE IS ROTATING.
TAILSTOCK
The tailstock can be adjusted along the lathe ways to accommodate different lengths of work. It mounts the “dead” center that supports the outer end of the work, and can be fitted with cutting tools for drilling, reaming and threading. The unit is clamped to the ways by tightening the CLAMP BOLT NUT. The spindle is positioned by rotating the HANDWHEEL and is locked in position with the BINDING LEVER.
CARRIAGE
The carriage includes the SADDLE, APRON, CROSS AND LONGITUDINAL FEED, SCREW CUTTING MECHANISM, COMPOUND REST and TOOL POST. The cutting tool is supported and its actions controlled by the carriage which is moved along the ways by hand or power feed. The power feed mechanism is located in the apron. A friction clutch controls longitudinal and cross power feeds. Half-nuts are engaged for thread cutting.
48 FEED MECHANISM
The feed mechanism transmits power through a train of gears to the QUICK CHANGE GEAR BOX, which regulates the amount of tool movement per revolution of the spindle . The feed mechanism also contains gears for reversing tool travel. Lettering on the INDEX PLATE tells how to position the levers for various thread cutting and feed combinations.
The LEAD SCREW transmits the power to the carriage through a gearing and clutch
arrangement in the apron. The FEED CHANGE LEVERS on the apron control the operation of power feeds and, when placed in neutral, permit half-nuts to be engaged for threading operations.
49
50
SAFETY RULES
1. Do not attempt to operate the machine until you are thoroughly familiar with it. When in doubt, secure additional instructions.
2. Wear appropriate clothing and goggles.
3. Get help to move any heavy attachment like the vise, dividing head, rotary table, etc. 4. Never handle a cutter with bare hands. Use a piece of heavy cloth for protection.
5. Use a small brush (or compressed air) to remove chips – NEVER BRUSH WITH YOUR HAND!
6. Stop the machine before attempting to remove chips. 7. Never reach over or near the rotating cutter.
8. Make sure the holding device is mounted solidly to the table and the work held firmly. Spring or vibration can cause thin cutters like the slitting saw to jam and shatter. 9. Do not talk to anyone while operating the machine, nor allow anyone to turn on your
machine for you.
10. No adjustments should be made while the cutter is rotating. Stop it before making measurements, removing chips, etc.
11. Keep the floor around the machine clear of chips and wipe up spilled cutting fluid immediately.
12. Be thoroughly familiar with the STOP lever.
13. Treat any small cuts and skin punctures as potential infections. Clean them thoroughly, apply antiseptic and cover with a bandage. Report any injury, even though minor, to your instructor.
14. Do not permit your work clothes to become saturated with oil and cutting fluids. Greasy clothing is a fire hazard.
15. Put all oily rags used to wipe down the machine in a metal container that can be closed tightly.
16. Do not fool around while operating the mill. Keep your mind on your job and be ready for any emergency.
52
COLUMN AND KNEE TYPE MILLING MACHINE
The column knee type milling machine is so named because the components that provide movement to the work consists of a COLUMN that supports and guides the KNEE in vertical movement. The knee supports the mechanism for obtaining cross traverse and longitudinal table movements: VERTICAL, CROSS, & LONGITUDINAL, all of which are controlled entirely by hand levers. All milling operations fall into two main categories:
1. FACE MILLING – The surface machined is parallel with the face of the cutter. Large flat surfaces are machined by this method.
2. PERIPHERAL MILLING – The surface being machined is parallel with the periphery of the cutter.
Milling cutters come in a large number of stock shapes, sizes, and kinds to meet many requirements. There are two general types:
1. SOLID CUTTER – The shank and body are made in one piece.
2. INSERTED TOOTH CUTTER – The teeth are made of special cutting material and are brazed or clamped into place. Teeth can be replaced.
Consult your instructor for the type of cutter needed.
There are two distinct cutting methods in milling operations:
1. CONVENTIONAL or UP-MILLING – The work is fed into the rotation of the cutter. The chip is at minimum thickness at the start of the cut and is so slight that the cutter has a tendency to slide until sufficient pressure is built up to make it bite into the work.
2. CLIMB or DOWN-MILLING – The work moves in the same direction as the rotation of the cutter. Full engagement of the tooth is instantaneous. The sliding action of conventional milling is eliminated resulting in a better finish and a longer life.
Climb milling is not recommended on light milling machines because lack of rigidity and light support offsets any advantages of the technique.
Care of Milling Cutters and Cutter Holding & Driving Devices 1. Support the cutter properly and hold the work rigid 2. Use the correct cutting speed and feed
3. An ample supply of cutting fluid is essential 4. Use the correct cutter for the job
5. Store cutters in individual compartments or on wooden pegs 6. Clean cutters before storing
7. Never hammer a cutter on the arbor. Examine the arbor for burrs or nicks if the cutter does not slip on easily
8. Use sharp cutters
To maintain accuracy during the machining operation it is necessary to prevent damage to the cutter holding and driving devices:
1. Keep the taper of the arbor free of nicks
2. Clean and lubricate the bearing sleeve and arbor support bearing before use
3. Clean the spacing collars before placing them on the arbor, otherwise cutter run-out will occur
53 4. Store arbors separately and in a vertical position
5. Never loosen or tighten the arbor nut unless the arbor support is locked in place 6. Use a wrench of the correct type and size
7. Do not tighten the arbor nut by striking the wrench with a hammer or mallet. This may crack the nut or distort the threats
8. To remove an arbor or adapter from the machine:
a. Loosen the nut on the draw-in bar a few turns. DO NOT remove it from the arbor completely
b. Tap the draw-in bar head with a lead hammer to loosen the arbor from the spindle c. Hold the loosened arbor with one hand and unscrew the draw-bar with the other d. Remove the arbor from the spindle, clean and store it
Cutting Speeds and Feeds, Fluids
The time required to complete a milling operation and the quality of the finish of the machined surface is almost completely governed by the CUTTING SPEED and FEED of the cutter.
Cutting Speed refers to the distance, measure in feet, a point (tooth) on the circumference moves in one minute. It is expressed in terms of FEET PER MINUTE (FPM) and is directly dependent on the REVOLUTIONS PER MINUTE (RPM) of the cutter.
Feed is the rate the work moves into the cutter and is given as FEED PER TOOTH PER
REVOLUTION (FTR). The selection of the proper feed is probably the most difficult thing for the machinist to determine. In view of the many variables; width of cut, depth of cut, condition of the machine and cutter, etc., feed should be as coarse as possible and consistent with the desired finish. Consult the mill manual or wall chart for the speeds and feeds required for various materials. Cutting Fluids serve several purposes. They carry away the heat generated during the machining operation, act as a lubricant and prevent the chips from sticking or fusing to the cutter teeth, and flush away chips. The lubricating qualities also influence the quality of the finish of the machined surface.
UNTIL YOU BECOME PROFICIENT IN THE USE OF THE MILL, CONSULT YOUR INSTRUCTOR OR SHOP PERSONNEL BEFORE STARTING ANY MACHINING! More information can be found in the reference book “Modern Metalworking”
54
55
Bench Grinder Safety Instructions
1. Always use goggles.
2. Never grind aluminum on the grinder. 3. Use the face of the wheel, not the sides.
4. Move the work back and forth across the face of the wheel. Even wear will result and prevent the wheel from becoming grooved.
5. Keep the wheel dressed and the tool rests properly adjusted.
6. Never put a wheel on the grinder before checking it for soundness. Destroy wheels that are not sound.
7. Never stand in front of the grinder when it is turned on. Stand on the side of the grinder until it reaches full speed. This will keep you clear of flying pieces if the wheel shatters.
8. Do not attempt to use the grinder unless the guards are in place.
9. Keep your hands clear of the rotating grinding wheel. It is a cutting tool and can cause serious injuries.
10. Never force the work into the grinding wheel.
